Stayed here last december for a city trip to Amsterdam. We were welcomed by very friendly owners in a beautiful house. We opted for the larger South Room, which was truly superb. The room overlooks the calm street. The room was large with a comfortable bed and a bathroom with all the comforts you need. We were the only couple there that weekend and chanced a sneak peek in the other room (the Terrace Room, sorry Diederik and Ian :p), which was also lovely and the terrace does allow you to have a smoke outside, but the bathroom seemed tiny.
The breakfast was very good, the bread was delicious, the fruit fresh and the huge selection of coffee was an adventure.
Diederik joined us at breakfast every morning for a couple minutes, giving us tips on what to do in Amsterdam, where to go and gave advice on good places to eat, which was very welcome.
From N29, it was about a 20 minute walk to the "Negen Straatjes" (Anne Frank House etc) and 15 minutes to the shopping streets.
We can really recommend a weekend at N29 and no doubt it'll be our first choice if we go back to Amsterdam.